A particular communication standard, i.e., IEEE Std 802.1Q, specifies the operation of virtual local area network (VLAN) bridges, which support VLAN operation within an IEEE 802 bridged LAN.
Multiple active paths between stations cause loops in the network. If a loop exists in the network topology, the potential exists for duplication of messages. When loops occur, some switches see stations appear on both sides of the switch. This condition confuses the forwarding algorithm and allows duplicate frames to be forwarded.
A Spanning-Tree Protocol (STP) prevents loops from being formed when switches or bridges are interconnected via multiple paths.
STP is a link management protocol that provides path redundancy while preventing undesirable loops in the network. For an Ethernet network to function properly, only one active path can exist between two stations.
To provide path redundancy, STP defines a tree that spans all switches in an extended network. STP forces certain redundant data paths into a standby (blocked) state. If one network segment in the STP becomes unreachable, or if STP costs change, the spanning-tree algorithm reconfigures the spanning-tree topology and reestablishes the link by activating the standby path.
Multiple Spanning Tree Protocol (MSTP) is a protocol that allows groups of VLANs to have different spanning tree topologies within an Ethernet Network. MSTP was introduced in IEEE 802.1s as amendment to 802.1Q, 1998 edition and adds the facility for VLAN bridges to use multiple spanning trees, providing for traffic belonging to different VLANs to flow over potentially different paths within the virtual bridged LAN. This allows for better load balancing and more efficient use of available resources.
In order to operate properly, the configurations must be identical on all switches. However, configuring MSTP on Ethernet switches can be a cumbersome and complex task, relying on a command-line interface (CLI) present on each individual switch.
The CLI is the primary user interface used for configuring, monitoring, and maintaining switch products. This user interface provides execution of entered commands, whether using a router console or terminal, or using remote access methods. It does, however, permit modification of only one switch at a time. Once an initial deployment of switches is performed, each time VLANs are added, moved, or deleted from an instance, each switch must again be accessed.
Accordingly, one of the large inhibitors of deploying MSTP is the complexity and tediousness of the deployment, plus the necessity to touch all devices in order to add a VLAN or instance of MSTP.